This invention relates to a vane compressor in which vanes can be smoothly moved radially outwardly at the start of the compressor.
A variable capacity vane compressor for use in air conditioners for automotive vehicles or the like has been proposed e.g. by Japanese Provisional Patent Publication (Kokai) No. 59-176492 assigned to the assignee of the present application, which has a rotor formed with vane slits in which associated vanes are slidably fitted, vane back pressure chambers each defined within a vane slit by the associated vane, a communication passage communicating between a discharge pressure chamber with the vane back pressure chambers, a valve arranged in the communication passage for opening the communication passage to introduce discharge pressure into the vane back pressure chambers when the discharge pressure within the discharge pressure chamber is lower than a predetermined value, and closing the communication passage when the former is higher than the latter, to thereby permit the vanes to be moved radially outward into close sliding contact with the inner peripheral wall of the cylinder at the start of the compressor and hence improve the startability of the compressor.
According to the proposed compressor, as shown in FIG. 1, the valve 60 is formed of a cylindrical ball-receiving bore 62, a ball 63 as a valve body received within the bore 62, a coiled spring 64 urging the ball 63 in a direction of opening the valve, and a stopper pin 65 for stopping the ball 63 in a valve opening position, whereby the valve 60 assumes the valve opening position and a valve closing position depending upon the discharge pressure within the discharge pressure chamber.
However, the ball-receiving bore 62 has a large axial length as compared with the diameter of the ball 63 so that there is a possibility of accumulation of oil in a gap between an outer surface portion of the ball 63 closer to the discharge pressure chamber and the inner wall of the bore 62. Consequently, even when the ball 63 is in the valve opening position, the gap between the ball 63 and the bore 62 is choked up with the accumulated oil, which obstructs introduction of the discharge pressure from the discharge pressure chamber into the vane back pressure chambers through the bore 62. As a result, the pressure within the vane back pressure chambers cannot rise to such a sufficient level as to cause the vanes to be moved out of the slits into close contact with the inner peripheral surface of the cylinder, often resulting in chattering of the vanes and degraded startability of the compressor.
Further, in order to eliminate variations in the valve closing characteristic such as valve closing pressure of the ball valve between individual ball valves, that is, in order to allow the valve to positively become closed when the discharge pressure reaches the predetermined value, the inner diameter of the ball-receiving bore 62 should be machined with close tolerances so as to provide an appropriate gap between the ball 63 and the bore 62. However, accurate machining of the bore 62 is difficult because of the large axial length of the bore 62, hence making it difficult to machine the receiving bore 62 to an appropriate inner diameter.